Solid-state magneto electrical transducer

ABSTRACT

A solid-state mechano-electrical transducer having means which is subject to a mechanical displacement when a magnetic force is applied and a solid-state element which converts the mechanical displacement into a variation in electrical quantity.

United States Patent 1 Yamada et al.

SOLID-STATE MAGNETO ELECTRICAL TRANSDUCER Inventors: Tadashi Yamada, Suita; Akio Y Yamashita, Ikeda; Masaru Tanaka, Toyonaka; Takehiro Tsuzaki, Osaka; Takashi Fujita, Toyonaka,

all of Japan Matsushita Electric Industrial Co., Ltd., Kadoma-shi, Osaka, Japan Filed: Nov. 8, 1971 App1.No.: 196,821

Related U.S. Application Data Continuation of Ser. No. 748,991, July 31, 1968, abandoned.

Assignee:

U.S. Cl ..317/235 R, 317/235 M, 317/235 H,

307/308, l79/l00.4l Int. Cl. ..H0ll 11/00, H011 15/00 Field of Search ..3l7/235-, 26, 23,.

317/234, 5.2, 5.3, 5.4; 307/308; 73/8855 D; l79/100.4l

Primary ExaminerJohn W. Huckert Assistant Examiner-Andrew J. James Attorney-Stevens, Davis, Miller & Mosher [57] ABSTRACT A solid-state mechano-electrical transducer having means which is subject to a mechanical displacement when a magnetic force is applied and a solid-state element which converts the mechanical displacement into a variation in electrical quantity.

3 Claims, 2 Drawing Figures PATENTEUJUH 5 ma 2' 3 E/VERG/Z/NG CURRENT (mA) Sv N R M mam M V 13 W 3 M0, M

/ ATTORNEY$ SOLID-STATE MAGNETO ELECTRICAL TRANSDUCER This is a continuation, of application Ser. No. 748,991, filed July 31, 1968 abandoned.

This invention relates to a solid-state device having means which is subject to a mechanical displacement in response to application of a magnetic force thereto and means for converting the mechanical displacement into a variation in electrical quantity.

Conventional devices having means which is subject to a mechanical displacement in response to application thereto of a magnetic force and means for converting the mechanical displacement into a variation in electrical quantity include electromagnetic relays and the like. An electromagnetic relay, for example, comprises an electromagnet which is operative to open or close electrical contacts thereby opening or closing an associated circuit. The electromagnetic relay having such incessantly opened and closed electrical contacts is defective in that the function of the electrical contacts is quickly deteriorated due to are discharge and other causes. I

A device which is called a reed relay is another typical example of the conventional transducers of the kind described above. The reed relay comprises two thin strips of ferromagnetic material enclosed in a very slightly spaced relation within a glass tube containing an inert gas and is operative in such a way that application of a magnetic field brings the thin strips into contact with each other thereby opening or closing an associated circuit. The reed relay as well as the electromagnetic relay thus having the function of opening or closing the spaced electrical contacts in response to energization by a magnetic force is defective in that its size becomes inevitably large.

Transducers employing a solid-state element such as a transistor or Esak i diode so that a mechanical displacement developed at the junction due to application of a magnetic force can be converted into a variation in an electrical quantity area further typical example of the conventional devices of the kind described above. However, these transducers are defective in that their sensitivity is quite poor and a large mechanical displacement is generally required in order to produce an appreciable variation in the electrical quantity.

It is therefore a primary object of the present invention to provide a novel solid-state mechano-electrical transducer which differs in its operating principle from that of the conventional devices described above and which is of a contactless structure, small in size and yet has a very high sensitivity. More precisely, the present invention contemplates the provision of a solid-state mechano-electrical transducer having means which is subject to a mechanical displacement in response to application thereto of a magnetic force and a solid-state element whose resistance value is variable depending on a pressure imparted thereto.

The above and other objects, features and advantages of the present invention will be apparent from the following description when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic vertical sectional view of an embodiment of the solid-state mechano-electrical transducer according to the present invention; and

0 electrical connections 2 and 2' provided adjacent to opposite ends of the solid-state element 1 for connection with lead wires, blocks 3 and 3' of magnetic material of cubic or like shape disposed above and beneath the solid-state element 1 in contact therewith, a cylindrical energizing coil 4 surrounding the magnetic blocks 3 and 3, and a base 5 on which the above elements are firmly mounted.

When now the magnetic blocks 3 and 3' are magnetized by the energizing coil 4, a pressure is imparted to the solid-state element 1 which is interposed between the magnetic blocks 3 and 3', and as a result, the resistance value of the solid-state element 1 is varied in inverse proportion to the pressure imparted thereto. Because of the above operating characteristic, the solidstate mechano-electrical transducer can find its useful applications in automatic control circuits, logic circuits, switches and other systems.

The solid-state element 1 which is an important component of the present invention will be described in detail.

The solid-state element 1 in accordance with the present invention is made by preparing a solid having a forbidden band such as a semiconductor or electrical insulator, introducing into the solid an impurity which forms a deep energy level within the forbidden band of the solid, and providing at least two electrical connections on the solid. The semiconductor described above may be any one of the known semiconductors including Ge, Si, GaAs, GaSb, GaP, CdS, Se, Cu O and PbO, while the insulator may be any one of the known insulators including BaTiO TiO and SiO. An impurity forming-a deep energy level is introduced into these semiconductors and insulators, but a suitable impurity must be selected depending on a specific semiconductor or insulator. For instance, an impurity such as Au, Cu, Fe, Mn, Ni or C0 is suitable for use when the semiconductor is Ge or Si, while an impurity such as Cu or 0 is suitable for use when the semiconductor is GaAs.

These impurities are added to the semiconductors and insulators by doping, diffusion on a similar method well-known in the art. The electrical connections may be either ohmic contacts or P-N junctions, but the sensitivity is better in the case of P-N junctions.

In the practical structure of the solid-state mechanoelectrical transducer embodying the present invention, N-type silicon having a specific resistance of 10 ohm cm is employed as the semiconductor and gold is diffused into the silicon as impurity. The amount of gold actually diffused into the silicon is controlled by the amount of plating, diffusion temperature, duration of diffusion and other factors. It is especially preferable to effect the diffusion in a hydrogen gas atmosphere in accordance with the method conventionally known in the art. Gold containing 0.8 percent by weight antimony is then deposited on the silicon substrate to provide alloy electrodes thereby to obtain the solid-state element 1. The energizing coil 4 and the magnetic blocks 3 and 3 forming the pressure imparting means of the transducer may be conventional energizing parts of a common electromagnetic relay.

One of the magnetic blocks is fixed to the base 5 and the solid-state element 1 is interposed between the magnetic blocks 3 and 3 to constitute the transducer of the present invention shown in FIG. 1.

FIG. 2 shows the electrical characteristic of the transducer according to the present invention, wherein the abscissa represents the energizing current in milliamperes and the ordinate represents the resistance value of the solid-state element in ohms. It will be apparent from FIG. 2 that the resistance value of the solid-state element decreases as the energizing current increases. In this connection, it will be understood that there are various other ways of impartation of the pressure by the utilization of magnetism and alternating current may be used depending on the way of pressure impartation.

It will be appreciated from the foregoing description that the solid-state mechano-electrical transducer according to .the present inventionwhich utilizes a magnetic force for the conversion of a mechanical displacement into a variation in an electrical quantity is advan tageous over conventional transducers in its contactless structure, small size and good responsiveness and thus finds useful applications in automatic control circuits, logic circuits, switches and other systems.

What is claimed is:

l. A solid-state electro-mechanical transducer sensitive to a magnetic field, said transducer comprising a solid-state element having the shape of a disk and made of a material having a forbidden band, said element containing an impurity forming a deep energy level in said forbidden band, a pair of electrodes connected to said element at positions remote from each other, and two cylindrical members of magnetizable material disposed on opposite surfaces of said element, and means for magnetizing said two members, wherein said members, when magnetized, cooperate to exert a compressive force on said element.

2. A solid-state transducer according to claim 1, in which said element is a semiconductor.

3. A solid-state transducer according to'claim l, in

which said element is an electrical insulator. 

1. A solid-state electro-mechanical transducer sensitive to a magnetic field, said transducer comprising a solid-state element having the shape of a disk and made of a material having a forbidden band, said element containing an impurity forming a deep energy level in said forbidden band, a pair of electrodes connected to said element at positions remote from each other, and two cylindrical members of magnetizable material disposed on opposite surfaces of said element, and means for magnetizing said two members, wherein said members, when magnetized, cooperate to exert a compressive force on said element.
 2. A solid-state transducer according to claim 1, in which said element is a semiconductor.
 3. A solid-state transducer according to claim 1, in which said element is an electrical insulator. 